A conventional holding device 60 for holding shanks of tools is disclosed in FIGS. 12 and 13, and generally includes a base 63 with a plurality of protrusions and the shank of a tool is held in the space 631 between the two adjacent protrusions 63. A plate 61 is installed to an inside of each of the protrusions except for the last one protrusion at the right end of the base 63, and a clamping member 611 having a toothed outer periphery is connected to an inclined section of the plate 61. The clamping member 611 is extended out from an elongate hole in the protrusion as shown. A rectangular friction plate is connected to each of the protrusion except for the first one protrusion on the left of the base 60, the friction plate faces the clamping member 611. The shank can be clamped between the clamping member 611 and the friction member.
Another conventional holding device known to applicant is disclosed in FIG. 14 and includes a base 70 with a plurality of protrusions 73 and the shank of a tool is held in the space 731 between the two adjacent protrusions 73. A plate 71 having an upright section 713 and an inclined section 711 is installed to an inside of each of the protrusions 73 except for the last one protrusion at the right end of the base 73, and a clamping member 72 having a toothed outer periphery is connected to the inclined section 711 of the plate 61 by connecting two wires 721 fixed on the clamping member 72 to the two slits 712 in the inclined section 711. The clamping member 72 is extended out from an elongate hole in the protrusion 73. A rectangular friction plate is connected to each of the protrusion 73 except for the first one protrusion 73 on the left of the base 70. The friction plate faces the clamping member 72. The shank can be clamped between the clamping member 72 and the friction member.
The structure of both two conventional holding devices is complicated and each part of the two conventional holding devices has to be made by specific machine and this makes the holding device be expensive which is not competitive in the market.
The present invention intends to provide a holding device having simple structure and able to hold shanks of tools of different sizes.